Many monitoring and control systems employ a plurality of sensors for measuring different parameters associated with a system. For instance, such sensed parameters include temperature, mechanical strain, pressure, as well as other. Traditionally, such sensors use mechanical and electrical principles for performing parameter sensing and measurement. For example, traditional temperature sensors employ thermocouples, thermistors, resistance temperature detectors (RTDs), and infrared sensors. Similarly, traditional strain sensors may include strain gauges, piezo-resistive pressure sensors, and capacitive pressure sensors.
Although such traditional sensors are useful in many applications, in other applications, such sensors may not be suitable. For instance, in applications where the sensing environment is harsh, such traditional sensors may not be suitable since they may degrade over time, or not work at all. For instance, in an underwater application, electronic-based sensors may not be suitable as the water generally causes shorts in the electronic components. Other harsh environments include corrosive environments, radiation environments, harsh chemical environments, high and low temperature environments, vacuum environments, and others potentially in combination.
One type of sensor useful for harsh environment sensing is an optical-based sensor that employs a Fiber Bragg Grating (FBG). A FBG sensor typically comprises an optical fiber that includes one or more FBG structures formed within the fiber. Each FBG structure is configured to reflect light at a particular wavelength (e.g., a narrowband wavelength range) and pass through light at other wavelengths. The FBG structure is sensitive to temperature (e.g., the structure expands and contracts with increasing and decreasing temperature, respectively) and to mechanical strain (e.g., the structure expands and contracts with strain). Accordingly, the wavelength of the optical signal that the FBG structure reflects depends on the stressed induced from applied strain, either caused by temperature and/or externally applied forces.
In the past, FBG-based sensors used a system to convert the reflected wavelength into a particular time of receiving the reflected signal. Accordingly, the time of receiving the signal is a function of the wavelength which, in turn, is a function of the sensed parameter (e.g., temperature, strain, pressure, etc.). Typically, such sensors employ a complex process for determining the time of receiving the reflected signal, which consists of converting the reflected optical signal into an electrical signal, digitizing the electrical signals, and performing an algorithm on the digitized signal for determining the peak of the signal. Such complex peak-searching algorithm and analog-to-digital conversion electronics generally limit the speed in which measurements may be made, as well as the number of FBG structures that may be employed on a single optical fiber.